Vitamin Supplements

Biology Poorly Established

Although most vitamins were discovered over 50 years ago, still very little is known about their biological role. Vitamins are clearly essential to life, yet the full range of their biological effects and their mechanism of action is poorly established. Nutritional immunology (the study of the role of vitamins and minerals in immunity) is still in its infancy and many unanswered questions remain. For instance, Vitamin A has a well characterized role in vision, where it serves a critical function as a signal mechanism between the retina and the initiation of nerve impulses. (Vitamin A deficiency, considered one of the most serious nutritional public health problems in the world, is the leading cause of preventable blindness, primarily among children in high risk areas, such as India and east Asia.) Yet vitamin A also has a role in cell differentiation and thus is important in immunity, although it is poorly understood. Furthermore, the biological connection between specific vitamin deficiencies and their diseases is also unknown. For example, riboflavin deficiency clearly causes cracked lips and tongue, but the biological pathway that leads to these symptoms is unknown. More puzzling still, vitamin deficiency diseases seem to manifest themselves differently in throughout the world for unknown reasons. For instance, thiamin deficiency is associated with peripheral nerve disease in Asia, but central nerve disease in the Western hemisphere. Much progress is needed in understanding the biological role of vitamins.

At Project Inform we do not always have the resources to produce our own material on every treatment topic. In this case we have tried to select quality information from reliable publications, but we cannot confirm that every fact in this handout is accurate. We encourage you to check out the publications from which this treatment information is taken; resource contacts are available through the hotline.

HIV-Related Deficiencies

Studies of nutrient levels in people with HIV find that they are either depleted, increased, or unchanged. These studies are difficult to interpret since they were not performed in a uniform manner and were often inadequately controlled. It is important to note that the literature on vitamin deficiencies does not even point in a consistent direction. Most discussion of vitamins, however, center on research that suggests nutrients are depleted, rather than unchanged or increased.

Overt signs of severe vitamin deficiency can be detected by clinical examination. However, most reported vitamin deficiencies in people with HIV are mild and subclinical, based primarily on variations from population norms in laboratory diagnosis. There are several confounding factors to consider when interpreting this level of deficiency.

Population norms of vitamin levels are sometimes based on estimated values, and thus may not be accurate. People with HIV may constitute a distinct population and may have different vitamin requirements than the normal, healthy population. Several studies indicate that metabolism may be altered in HIV disease, possibly changing nutrient requirements. However, no studies have been performed that demonstrate unique nutrient requirements in people with HIV. Correlating mild deficiencies to clinical signs or increased risk of disease is difficult and poorly established. According to the published reports, mild laboratory-diagnosed deficiencies may indicate early signs of progressive malnutrition, a response to specific infections, nutrient-drug interactions, altered metabolism, inadequate diet, or random errors on imperfect lab tests. Although all these conditions have been documented in people with HIV, it is unknown to what degree they each contribute to specific nutrient deficiencies on an individual level.